Population Growth Models & Dynamics

Vocabulary flashcards covering key terms and concepts related to population growth models, dynamics, and limiting factors.

Population equilibrium

A state in which a population is neither growing nor shrinking; births + immigration equal deaths + emigration.

Carrying capacity (K)

The maximum number of individuals an environment can support indefinitely without resource depletion.

Growth rate

The amount a population changes divided by the time over which the change occurs.

Constant growth

An idealized, rare pattern where a population adds a fixed number of individuals per unit time, producing a straight-line graph.

Exponential growth

Growth at a constant percentage rate per unit time, yielding a J-shaped curve that is ultimately unsustainable.

Logistic growth

Growth that starts exponentially but slows as carrying capacity is approached, producing an S-shaped curve.

Population size

The total number of individuals in a population.

Population density

The number of individuals per unit area or volume.

Population growth curve

A graph showing how a population’s size changes over time.

Intrinsic rate of increase (r or rmax)

The maximum per-individual growth rate of a population under ideal conditions.

Net reproductive rate

Percentage population growth after accounting for births and deaths over a specified time period.

Doubling time

The constant period required for a population growing exponentially to double in size.

J curve

Graphical representation of exponential growth in which population size accelerates upward.

S curve

Graphical representation of logistic growth; population size plateaus near carrying capacity.

Population explosion

A rapid, exponential increase in population size due to favorable conditions.

Boom-bust cycle

A pattern where a rapid population increase (boom) is followed by a sharp decline (bust) after exceeding carrying capacity.

Population crash

A sudden, steep decline in numbers when a population overshoots carrying capacity.

Biotic potential

The maximum reproductive capacity of a species under ideal conditions, measured by r.

Environmental resistance

Biotic and abiotic factors that limit population growth by increasing mortality or reducing reproduction.

r-selected species (r-strategists)

Species that reproduce quickly, produce many offspring with little or no parental care, and often show boom-bust dynamics.

K-selected species (K-strategists)

Species that reproduce slowly, invest heavily in parental care, have high offspring survival, and fluctuate around carrying capacity.

Recruitment

The proportion of offspring that survive to reach reproductive age in a population.

Type I survivorship

Life-history pattern with low early mortality and most individuals living to old age (e.g., humans, elephants).

Type II survivorship

Pattern with roughly constant mortality throughout life (e.g., squirrels, some birds).

Type III survivorship

Pattern where many offspring die young and few reach adulthood (e.g., insects, many plants).

Density-dependent factor

A factor whose impact on population growth increases with population density (e.g., disease, food shortage, predation).

Density-independent factor

A factor that affects population growth regardless of density (e.g., fire, extreme temperature).

Top-down control

Population regulation by consumers at higher trophic levels, such as predators or parasites.

Bottom-up control

Population regulation determined by resource availability at lower trophic levels, such as producers or nutrients.

Critical number

The minimum population size required for a species to recover and maintain viability.

Immigration

The movement of individuals into a population from another population, contributing to growth.

Emigration

The movement of individuals out of a population to another population, contributing to decline.